Stereotactic surgery is a minimally invasive form of surgical intervention that uses a three-dimensional (3D) coordinate system to locate intra-cerebral target sites to perform various surgical procedures. Frame-based stereotactic surgery uses a head frame that place the head of a subject in a fixed position with reference to the 3D coordinate system. Surgical instruments that attach to the head frame can be adjusted to the 3D coordinates of the target site so that the target site is accurately approached by the surgeon. Frameless stereotactic surgery relies on fiducial markers that are adhered to the subject's scalp before the brain is imaged. In the operating room, the orientation of these markers is used to register a computer containing certain brain images. Once registration is completed, the computer shows the relationship between the surgical instruments and the imaged brain.
Whether using a frame-based or frameless approach, an incision may be made in the scalp to expose the patient's skull once the target site has been accurately located. After forming a burr hole in the skull, a medical device can be inserted into the subject's brain and implanted at the target site. If a surgical revision is necessary, the indwelling medical device has to be removed and the trajectory reassessed for implanting a medical device at the target site again. Such a process is time consuming and costly.